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Creatinine, Serum / Plasma
|Performed by||Parnassus & Mt. Zion Chemistry|
|In House Availability||Test available 24 hours per day 7 days per week|
|Method||Spectrophotometric, kinetic (alkaline picrate,Jaffe) assay on Beckman DXC 600/800 analyzers. Calibration traceable to isotope dilution mass spec (IDMS) standardization
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|Container type||Gold top or Light Green top|
|Amount to Collect||1 mL blood Click here for Microdetermination info|
|Sample type||Serum or plasma|
|Preferred volume||0.5 mL serum or plasma|
|Min. Volume||0.2 mL serum or plasma Click here for Microdetermination info|
|Units||Creatinine: mg/dL, eGFR in mL/min/1.73 m2|
|Normal range|| Creatinine:
1. Pediatric reference ranges adapted from Beckman's published "Pediatric Reference Range Guidelines for Synchron Systems, Bulletin 9345.
2. Normal range for adults was determined by testing 270 male and female healthy blood donors at UCSF.
|Synonyms||GFR; eGFR; glomerular filtration rate|
|Stability||Room temperature 8 hours, refrigerated 2 days, frozen at -20C 1 week|
|Turn around times||STAT 1 hour, Routine 4 hours|
|Additional information||To convert mg/dL to µmol/L (SI units) multiply by 88.4.
Ketones may artifactually increase results. Small to moderate ketones (40-80 mg/dl acetoacetic acid) may increase creatinine results by approx. 0.5 mg/dL; large amounts (> 125 mg/dL acetoacetic acid) may increase results approx 1 mg/dL, and very large amounts (> 400-500 mg/dL) may increase results more than 3 mg/dL.
Estimated GFR (eGFR) is reported with serum creatinine results in adults and is determined using the Modification of Diet in Renal Disease (MDRD) formula (traceable to isotope dilution mass spec IDMS calibration):
eGFR (mL/min/1.73 m2) = 175 x (Scr)-1.154 x (Age)-0.203 x (0.742 if female) x (1.212 if African American)
Because the MDRD formula is not considered sufficiently accurate for estimating GFR in patients with normal or mildly reduced renal function, results greater than 60 mL/min/1.73 meters squared body surface area are displayed as > 60 mL/min and are not reported as an exact number. Note that the estimated GFR result is not reliable in certain groups including severely ill patients. The MDRD equation used to estimate GFR has been validated only in Caucasian and African Americans 18 – 70 years of age. The equation has not been validated in other population groups, pregnant women, transplant recipients, medically unstable patients including those with acute renal failure, or in persons with extremes of body size, muscle mass, or nutritional status. Application of the MDRD calculation in these cases may lead to errors in GFR estimation. Click here for more information on this topic
GFR can also be estimated from serum creatinine in adults by the older formula of Cockcroft DW, Gault MH: (Nephron 1976;16:31) :
For women, multiply the calculated result by 0.85
Note that the Cockcroft-Gault formula is susceptible to many of the same limitations of the MDRD formula and may overestimate GFR by 16% or more when using current methods of creatinine measurement.
According to the National Kidney Disease Education Program, the best equation for estimating glomerular filtration rate (GFR) from serum creatinine in children is the Bedside Isotope Dilution Mass Spectrometry (IDMS)-traceable Schwartz equation
Bedside IDMS-traceable Schwartz Equation for Children
GFR (mL/min/1.73 m2) = (0.41 x Height in cm) / Creatinine in mg/dL)
|Last Updated||10/4/2013 10:06:11 PM|
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